Machines designed to clean semiconductor wafers, magnetic memory disks, and other delicate workpieces are generally well known. In the manufacture of integrated circuits, semiconductor wafer disks are sliced from a silicon ingot and thereafter prepared for further processing. After each wafer is sliced from the ingot, it is typically cleaned. rinsed, and dried to remove debris from its surfaces. Thereafter, a series of steps are performed on the wafer to build the integrated circuits upon its surface, including the application of a layer of microelectronic structures and the application of a dielectric layer.
Magnetic memory disks, flat panel displays, and other workpieces may also require cleaning or washing during processing. Accordingly, methods and apparatus for quickly and efficiently cleaning such workpieces are needed. A conventional semiconductor wafer cleaning machine utilizes several polyvinyl acetate (PVA) cleaning elements that perform mechanical contact scrubbing of the wafer surfaces during a cleaning process. Unfortunately, treatment time may be undesirably long because each wafer must pass through a number of cleaning elements in a serial manner. The use of a number of cleaning elements adds to the time and cost associated with the cleaning procedure and increases the maintenance cost associated with the cleaning equipment.
Resilient cleaning elements for semiconductor wafers, memory disk elements, flat panel displays and the like may become contaminated with debris or particulate that are liberated from the surfaces of the workpieces as they are cleaned. Such cleaning elements may become embedded with small particles that are difficult to remove by rinsing or cleaning solutions during the cleaning procedure. Accordingly, such cleaning elements must either be periodically cleaned (during downtime of the cleaning machine) or replaced to ensure that the sensitive workpieces are not damaged by such embedded debris.
Vibrational or ultrasonic cleaning tanks and associated cleaning procedures are well known. Conventional ultrasonic tanks vibrate at an ultrasonic frequency to agitate the cleaning solvent contained within the tank. The ultrasonic vibration within the solution enhances cleaning of the workpieces submerged in the solution by loosening the debris from the workpiece surface. However, while such prior art ultrasonic tanks effectively employ ultrasonic energy, they fail to take advantage of the mechanical vibrations that can otherwise be utilized to reduce the time associated with cleaning workpieces by conventional contact scrubbing or ultrasonic cleaning alone.